The mammalian periodontium is a unique support structure that anchors teeth in the jaw bone by providing firm attachment and resilient responsiveness to pressures. Much of the resilient properties of the periodontium are facilitated by a non-mineralized periodontal ligament (PDL) that connects the root surface with the alveolar bone. Recent studies from our laboratory have suggested that ameloblastin (AMBN) was 300-fold upregulated during periodontal remodeling (Holliday et al. 2005, Luan et al. 2007). In addition, we have localized AMBN in Hertwig's Epithelial Root Sheath (HERS) and revealed an inhibitory effect of AMBN on PDL mineralization and crystal formation in solution and gels. Our K14 promoter-driven, AMBN overexpressing transgenic mouse model featured a robust periodontal phenotype with changes in root cementum surface structure, cervical alveolar bone height, periodontal ligament width, and altered enamel structure compared to wild-type controls. Our findings were underscored by clinical studies that have shown a positive effect of enamel matrix derivatives (EMD) on the prevention of ankylosis (Iqbal and Bamaas 2001, Filippi et al. 2001) and by ameloblastin and amelogenin gene knockout models displaying evidence of PDL hypercalcification (Fukomoto et al. 2004, Hatakeyama et al. 2006). Together, these preliminary studies provide the basis for a research plan in which we will address the question whether AMBN is a unique HERS product involved in periodontal development and mineral homeostasis. Proposed studies are designed to explore and develop novel clinical aids to the benefit of Millions of Americans suffering from periodontal disease. PUBLIC HEALTH RELEVANCE: One of the most unique features of tooth gums is the elastic but firm attachment of tooth roots to the jaw bone. Here we will conduct a series of studies to investigate the effect of a unique gene product (called ameloblastin) in the formation of tooth attachment. These studies might eventually lead to novel cures for gum diseases.